Abstract
Absence of high-molecular-weight glutenin subunit (HMW-GS) Dx2 weakens the gluten quality, but it is unclear how the absence of Dx2 has these effects. Thus, we investigated the gluten quality in terms of cytological, physicochemical, and transcriptional characteristics using two near-isogenic lines with Dx2 absent or present at Glu-D1 locus. Cytological observations showed that absence of Dx2 delayed and decreased the accumulation of protein bodies (PBs), where fewer and smaller PBs formed in the endosperm. The activity and gene expression levels of nitrogen assimilation and proteolysis enzymes were lower in HMW-D1a without Dx2 than HMW-D1p with Dx2, and thus less amino acid was transported for protein synthesis in the grains. The expression pattern of genes encoding Glu-1Dx2+1Dy12 was similar to those of three transcription factors, where these genes were significantly down-regulated in HMW-D1a than HMW-D1p. Three genes involving with glutenin polymerization were also down-regulated in HMW-D1a. These results may explain the changes in the glutenin and glutenin macropolymer (GMP) levels during grain development. Therefore, we suggest that the lower nitrogen metabolism capacity and expression levels of glutenin synthesis-related genes in HMW-D1a accounted for the lower accumulation of glutenin, GMP, and PBs, thereby weakening the structural‒thermal properties of gluten.
Highlights
Wheat grain proteins are classified as albumins, globulins, gliadins, and glutenins based on their solubility properties
We found that the expression patterns of TaGAMyb, TaPBF, and TaSPA were similar to that of Glu-1Dx2+1Dy12 (Figure 7B-D), thereby indicating these three transcription factors (TFs) up-regulated the expression of high-molecular-weight glutenin subunit (HMW-glutamine synthetase (GS)) genes, as indicated by Ravel et al [12]
We investigated the effects of the absence of Dx2 on the gluten quality of wheat based on cytological, physicochemical, and transcriptional analyses using two near-isogenic lines (NILs) with HMW-GS Dx2 absent or present at the Glu-D1 locus
Summary
Wheat grain proteins are classified as albumins, globulins, gliadins, and glutenins based on their solubility properties. The effects of these TFs on glutenin accumulation in wheat with different HMW-GSs according to the Glu-D1 locus have not been elucidated. The high level expression of genes encoding PPIase, SUMO1, and PDI enhances the folding of storage proteins during grain-filling, thereby leading to the accumulation of more glutenin macropolymers (GMPs) [11,21,23]. The effects of the absence or presence of single HMW-GSs on the folding and assembly of glutenin during grain development are unclear. We analyzed the accumulation of storage proteins, the activities and gene expression levels of nitrogen metabolism enzymes, and the expression of genes related to glutenin synthesis and folding during grain development. Results followed by a different letter in the same column are significantly different (p < 0.05)
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